We have included these definitions for you,
not to confuse you but to familiarize you with
our industry's terminology and lingo.
* Accurator: A piston type metering device that feeds the proper amount of liquid refrigerant into the
* AFUE : Stands for Annual Fuel Utilization Efficiency. This is a percentage measurement of a furnace’s
heating efficiency. For example, an AFUE of 90 means that 90% of the fuel is being used to warm your
home, while the other 10% escapes as exhaust with the combustion gases. The U.S. Department of
Energy”s minimum efficiency level is 78%. The higher the AFUE, the more efficient the furnace.
* Air Change: The amount of air required to completely replace the air in a room or building; not to be
confused with re-circulated air.
* Air Conditioner: A device or system which delivers simultaneous control of air temperature, relative
humidity, purity, and motion.
* Air-Cooled System: A type of air conditioning system that uses freon as a refrigerant and air as a
condensing medium. A fan discharges heat from the condenser coil to the outdoors. Typically, the air-
cooled condenser is located outside and refrigerant lines are piped to it from the indoor unit.
* Air Diffuser: An air distribution outlet or grille designed to direct airflow into desired patterns.
* Air Handler: The portion of the central air conditioning or heat pump system that forces heated or
cooled air through your home’s ductwork. In some systems a furnace handles this function. Also
known as a fan-coil.
* Ambient Temperature: The air temperature (usually the outdoor air temperature) surrounding the
heating or cooling equipment.
* ARI: Stands for Air-Conditioning and Refrigeration Institute, a non-profit, voluntary organization
comprised of heating, air conditioning and refrigeration manufacturers. ARI publishes quality
standards for testing and rating heat pumps and air conditioners to provide you with a standardized
measure of comparison.
* Atmospheric Pressure: The weight of a 1 square inch column of the earth’s atmosphere. At sea
level, atmospheric pressure is 14.696 pounds per square inch.
* Auto Changeover: A control package that allows you to automatically switch from a primary air
conditioning system to a backup in the event of the primary system’s failure.
* Balance Point: An outdoor temperature, usually between 30° F and 45° F, at which a heat pump’s
output exactly equals the heating needs of the home. Below the balance point, supplementary electric
heat is needed to maintain indoor comfort.
* Blower: An air handling device for moving air in a distribution system.
* Boiling Point: The temperature at which the addition of any heat will begin a change of state from a
liquid to a vapor.
* BTU: Stands for British Thermal Unit — the amount of heat required to raise the temperature of one
pound of water by one degree (Fahrenheit). Used to describe a device’s heating or cooling capacity.
One BTU is approximately equal to the heat given off by a wooden kitchen match.
* BTUh: The abbreviation for British Thermal Units per Hour. A common measure of heat transfer rate.
* Capacity: The ability of a heating or cooling system to heat or cool a given amount of space. For
heating, this is usually expressed in BTUs. For cooling, it is usually given in tons.
* Carbon Monoxide (CO): A colorless, odorless gas produced by burning any fuel. Old and
malfunctioning heating systems produce high volumes of this gas. CO is highly toxic and potentially
deadly. Symptoms of CO poisoning are similar to those of the flu: headaches, fatigue, shortness of
breath, nausea and dizziness. The Consumer Product Safety Commission recommends annual
inspections for carbon monoxide.
* CFM: Stands for Cubic Feet per Minute. Commonly used to measure the rate of air flow in an air
conditioning system. The higher the number, the more air is being forced through the system.
* Central Air Conditioner System: System in which air is treated at a central location and carried to
and from the rooms by one or more fans and a system of ducts.
* Centrifugal Compressor: A type of compressor used in vapor compression refrigeration cycles
where a rotating impeller is the device which compresses the refrigerant vapor. The vapor is drawn into
the impeller axially, and is discharged radially after energy is added to the vapor within the impeller.
* Centigrade: A temperature scale with the freezing point of water at 0 degrees and the boiling point at
100 degrees at sea level. Also known as the Celsius scale.
* Charge: The amount of refrigerant in a system.
* Chilled Water System: A type of air conditioning system that has no refrigerant in the unit itself. The
refrigerant is contained in a remotely located chiller which chills and then pipes the refrigerant to the air
* Comfort Air Conditioning: An A/C system designed for the comfort of people, not the protection of
computer-based electrical systems. Computers and other high-tech equipment usually require an
extremely low humidity environment — far lower than people require intheir homes.
* Compressor: Part of a split-system heat pump or air conditioner’s outdoor unit that controls the
pressure applied to the refrigerant so that it can circulate. It plays a vital role in taking in heat to warm
your home with a heat pump or getting rid of heat to keep your home cool.
* Compression: The reduction of volume of a vapor or gas by mechanical means.
* Compression Ratio: The ratio determined by dividing the discharge pressure by the suction
pressure in PSI (pounds per square inch).
* Condensation Point: The temperature at which the removal of any heat will begin a change of state
from a vapor to a liquid.
* Condenser: A device that transfers unwanted heat out of a refrigeration system to a medium that
absorbs the heat and transfers it to a disposal point. There are three types of condensers: air-cooled
condensers, water-cooled condensers, and evaporative condensers. Most residential systems have
an air-cooled condenser.
* Condenser Coil: A series of tubes filled with refrigerant, normally located outside the home, that
removes heat from the hot, gaseous refrigerant so that it becomes liquid again.
* Condensing Unit: Part of a refrigerating mechanism which pumps vaporized refrigerant from the
evaporator, compresses it, liquefies it in the condenser and returns it to the refrigerant control. It’s the
outdoor section of a split system air conditioner or heat pump.
* Cooling Capacity: A measure of the ability of a unit to remove heat from an enclosed space.
* Cooling Load: Heat which flows into a space from outdoors and/or indoors.
* COP: Stands for Coefficient of Performance. A ratio that compares a heat pump system’s heating
efficiency to that of electric heat. For example, a heat pump system with a COP of 3.0 provides heat at 3
times the efficiency of electric heat. A heat pump’s system COP will decrease as outdoor temperatures
drop, eventually providing little or no efficiency advantage over electric heat – and that’s the point when
your auxiliary heat kicks in to heat your home.
* Damper: A valve or movable plate used in duct work that opens or closes to control airflow. Used in
zoning to regulate the amount of warm or cool air entering certain rooms in your home.
* DB: Stands for Decibels. A unit measuring the intensity of noise.
* Defrost Cycle: The process of removing ice or frost buildup from the outdoor coil during the heating
* Dehumidification: The reduction and removal of water vapor in air by cooling the air below the dew
* Direct Expansion Systems: One of two types of basic cooling media (the other is chilled water).
Direct expansion systems utilize freon for cooling and dehumidification. The three most common
methods of heat rejection are air cooled, water cooled and glycol cooled.
* Direct Vent: An opening that pulls in outside air for combustion and expels combusted gases directly
* Downflow Air Conditioner: A type of precision air conditioning system that discharges air downward,
directly beneath a raised floor. Commonly found in computer rooms and modern office spaces.
* Downflow Furnace: A type of furnace that takes cool air from the top and blows warm air to the
bottom. Commonly used where furnaces must be located in a second-floor closet or utility area.
* Duct: A hollow pipe or closed conduit made of sheet metal, fiberglass board, or other suitable
material used for carrying heated or cooled air to and from an air handling unit to the vents in your
* EER: Stands for Energy Efficiency Ratio — a measurement of the efficiency with which a product uses
energy to function. It is calcuated by dividing a product’s BTU output by its wattage.
* Efficiency: A rating on comfort equipment, similar to the miles per gallon rating on your car. The
higher the rating, the more efficient the system and the lower your fuel consumption will be.
* Electronic Air Cleaner: An electronic device that filters out large particles and contaminants in indoor
* Emergency Heat: The back-up heat built into a heat pump system. Also known as supplemental or
* Energy Saver Switch: A switch that causes an air conditioner’s fan and compressor to cycle on and
off together, reducing energy consumption.
* ENERGY STAR: A government program that helps businesses and individuals protect the
environment through superior energy efficiency. Products earn the Energy Star rating by meeting strict
anti-polution and energy-efficiency guidelines set by the Environmental Protection Agency and the
Department of Energy. Products with the Energy Star rating will help you use less energy and save on
* Evaporator Coil: Part of a split-system air conditioner or heat pump located inside the home. A series
tubes filled with refrigerant cools and dehumidifies the air by converting liquid refrigerant into a gas (or
vice-versa). A blower motor then moves air over the coil to either heat or cool your home. It is also
known as a cooling coil, blower coil, chilling unit or indoor coil.
* Fahrenheit: The scale of temperature measurement most commonly used in the United States of
America. In this scale, water freezes at 32 degrees and boils at 212 degrees.
* Fan Coil: An indoor component of an air conditioner or heat pump system, used in place of a furnace
and evaporator coil, to provide change the refrigerant from a gas to a liquid (or vice-versa) and blow air
over the coil to cool or heat your home.
* Filter: A device used to remove dust and other particles from air to provide healthier air quality and to
protect the HVAC equipment. The higher the MERV rating, the better the filter.
* Free Cooling System: A water- or glycol-cooled system with an additional coil that provides chilled
water cooling when the outdoor ambient temperature is cold, thereby reducing or eliminating
compressor operation. Provides efficient cooling in Northern climates.
* Freon: A general term used to identify, any of a group of partially or completely halogenated simple
hydrocarbons containing fluorine, chlorine or bromine, which are used as refrigerants. R-22 is the
most well-known and used of these refrigerants; it will be phased out in the coming years.
* Furnace: The part of a heating system which converts gas, oil, electricity or other fuel into heat for
distribution within a structure.
* Glycol-Cooled System: A type of air conditioning system that uses freon as a refrigerant and a
water/glycol solution as a condensing medium. Typically, the glycol-cooled condenser is located inside
the air conditioner with the rest of the refrigeration components. The glycol keeps the solution from
freezing during winter operation.
* GPH: Stands for Gallons Per Hour. An efficiency rating for oil furnaces.
* Ground Water-Source: Water from an underground well is being used as the heat source or heat
sink for a heat pump.
* Heating Capacity: The rate at which a specific device can add substantial heat to a substance,
expressed in BTUh (British Thermal Units per hour).
* Heat Exchanger: The part of a furnace that transfers heat energy from the source to a conveying
* Horizontal Furnace: A type of furnace that lies on its side. It draws in air from one side, heats it and
sends the warm air out the other side. Most often used in attics or crawl spaces.
* Heat Gain: The amount of heat gained, in BTU’s, from a space to be conditioned, at the local summer
outdoor design temperature and a specified indoor design condition.
* Heat Loss: The amount of heat lost, in BTU’s from a space to be conditioned, at the local winter
outdoor design temperature and a specified indoor design condition.
* Heat Pump: A unit that both cools and heats your home. It works just like an air conditioner in cooling
mode; however, in heating mode, the refrigerant flow is reversed and heat is extrated from the outside
air too heat your home. A heat pump system can be either a split system or a packaged system.
* Heat Transfer: The movement of heat from one place to another, between two substances, or within
* Humidity: The amount of moisture in the air. Air conditioners remove moisture for added comfort.
* Humidifier: A piece of equipment that adds water vapor to heated air as it moves out of the furnace.
This adds necessary moisture to protect your furnishings and reduce static electricity.
* Humidistat: A device designed to regulate humidity input by reacting to changes in the moisture
content of the air.
* HSPF: Stands for Heating Seasonal Performance Factor. A measure of the heating efficiency of a
heat pump. It’s calculated by dividing the heat pump’s total heating output (BTUh) by electrical wattage
per hour. The higher the HSPF number, the more efficiently the heat pump heats your home.
* HVAC: Stands for Heating, Ventilating and Air Conditioning. The initials are often used to describe the
industry that produces and services home comfort equipment.
* Hybrid Heat System: A fuel-saving alternative to traditional heating and cooling systems that
combines a furnace with a heat pump. A Hybrid heat system reacts to changing temperatures and
automatically adjusts to the most efficient energy saving method available to heat or cool a home.
Hybrid Heat is adaptable for gas or electric systems and by using a variable speed fan hot or cool air is
distributed consistently and evenly throughout a home.
* Indoor Unit: This is usually located inside the house and contains the indoor coil, fan, motor, and
filtering device, sometimes called the air handler.
* Insulation: Any material that slows down the transfer of heat.
* Integrally Controlled Motor: A variable-speed motor that operates at low RPM when possible for
maximum efficiency and quiet operation. ICM motors are more than 90% efficient versus 60% efficiency
for conventional motors.
* Isolation Valves: Valves used for the transfer and isolation of refrigerant charge in the cooler or
condenser, allowing refrigerant to be stored inside a chiller during servicing.
* (K) Factor: The insulating value of any material. Also known as conductivity.
* Kilowatt (kW): A measurement of the energy output of a device. Equal to 1,000 watts.
* Kilowatt-Hour (kWh): A common unit of electrical consumption measured by the total energy created
by one kilowatt in one hour.
* Load Calculation: A series of measurements and studies used to analyze and determine the heating
or cooling requirements of your home so that properly sized air conditioning and heating equipment
may be installed. This calculation uses information such as the square footage of your home, window
or door areas, insulation quality and local climate to determine the heating and cooling capacity
needed by your furnace, heat pump or air conditioner.
* Low Boy: A type of furnace configuration in which the furnace is lower in height and occupies more
* Matched System: A heating and cooling system comprised of products that have been certified to
perform at promised comfort and efficiency levels when used together, and used according to design
and engineering specifications.
* MERV: Stands for Minimum Efficiency Reporting Value. A measurement of air filter’s ability to remove
particlesfrom 3 to 10 microns in size. The MERV scale ranges from 1 (least efficient) to 16 (most
* Microprocessor Controls: A air conditioning control system that uses computer logic to maintain
precise control of temperature and humidity and to monitor the unit’s operation.
* Natural-Draft Furnace: A furnace in which the natural flow of air from around the furnace provides the
air to support combustion.
* Outdoor Coil/Condensing Unit: The portion of a heat pump or central air conditioning system that is
located outside the home and functions as a heat transfer point for collecting heat from and dispelling
heat to the outside air.
* Packaged System: A self-contained heating and/or air conditioning system which has all
components located in one cabinet. It is placed outside the home – on the ground, on the roof, or
sometimes mounted through the walls of the building.
* Payback Analysis: An overall measure of the efficiency and value of your home comfort system. By
combining your purchase price and ongoing operating costs, a payback analysis determines the
number of years required before monthly energy savings offset the purchase price.
* Purge Device: A device which removes air and water vapor from the refrigerant inside a chiller.
* Puron: An environmentally sound refrigerant designed not to harm the earth’s ozone layer. Federal
law requires that all manufacturers phase out ozone-depleting refrigerants in the next few years. Puron
Refrigerant has been approved by the US Environmental Protection Agency as a replacement for Freon
R-22 and other ozone depleting refrigerants.
* R-22 Refrigerant: An ozone-depleting, hydrochlorofluorocarbon (HCFC) refrigerant that has been the
refrigerant of choice for residential heat pump and air-conditioning systems for decades. Because of
its potentially harmful environmental effects, production of R-22 and systems that use it are being
phased out and will cease in 2015.
* Reciprocating Compressor: A type of compressor used in air conditioners that compresses
refrigerant through a piston action.
* Recycling: The removing, cleaning and reusing of refrigerant.
* Refrigerant: A substance that produces a rcooling effect while expanding or vaporizing.
* Refrigerant Lines: Two copper lines that connect an air conditioning system’s condenser coil (the
outdoor unit) to the evaporator coil (the indoor unit).
* Register: A combination grille and damper assembly covering an air opening or end of an air duct.
* Relative Humidity: The ratio of the amount of vapor contained in the air to the greatest amount the air
could hold at that temperature. Normally expressed as a percentage.
* Return Air: Air drawn into a heating unit after having been circulated from the heater’s output supply
to a room.
* Reversing Valve: A device in a heat pump that reverses the flow of refrigerant as the system is
switched from cooling to heating.
* Scroll Compressor: A specially designed compressor that works in a circular motion vs. an up and
down piston action.
* SEER: Stands for Seasonal Energy Efficiency Ratio. A rating that denotes the efficiency of air
conditioning equipment. It is the amount of cooling your equipment delivers for every dollar spent on
electricity. It is the ratio of cooling delivered by a system (measured in BTUs) to the dollar cost of the
electricity to run the system (meaured in , as measured in watt-hours. The higher the SEER, the more
efficient the unit. The more efficient the unit, the lower the operating cost. The U.S. Government’s
minimum SEER is 10 for split systems and 9.7 for packaged units.
* Setback Thermostat: A state-of-the-art electronic thermostat with a built-in memory that can be
programmed for different temperature settings at different times of the day.
* Single Package Product: A year-round heating and air conditioning system that has all of the
components completely encased in one unit outside the home.
* Split System: A central air conditioning or heat pump system consisting of two or more major
components. The system usually consists of a compressor-containing unit and condenser (installed
outside the house) and a non-compressor-containing air handling unit (installed within the building).
This is the most common type of system installed in a home.
* Storage Tank: A steel shell where the refrigerant charge for a chiller may be temporarily stored while
the chiller is serviced.
* Supercooled Liquid: Liquid refrigerant cooled below its saturation point.
* Subcooler: This is a section of some condensers in which the temperature of the condensed
refrigerant liquid is reduced. This improves the energy efficiency of the chiller.
* Superheated Vapor: Refrigerant vapor heated beyond its saturation point.
* Superheating: Creating a rise in temperature by adding heat energy to a refrigeration vapor.
* Switchover: A device in a heat pump that reverses the flow of refrigerant as the system is switched
from cooling to heating.
* Temperature: The measure of the intensity of heat that a substance possesses.
* Thermidistat: A sophisticated, programmable thermostat that senses the outdoor temperature,
indoor air temperature, and indoor relative humidity. A built-in microprocessor determines the most
efficient way to achieve ideal comfort.
* Thermostat: A temperature control device, typically found on a wall inside that consists of a series of
sensors and relays that monitor and control the functions of a heating and cooling system.
* Thermostatic Expansion Valve: A precision device used to meter the flow of liquid refrigerant
entering the evaporator at a rate that matches the amount of refrigerant being boiled off in the
* Ton (or Tonnage): Not 2000 lbs, but a unit of measure used to describe the cooling capacity of an air
conditioning system. One ton of cooling is based on the amount of heat needed to melt one ton (2000
lbs.) of ice in a 24 hour period (equal to 12,000 BTUh).
* Two Stage Compressor: Two Stage Compressors are capable of two levels of operation, a low
stage and a high stage. Properly sized equipment will operate 80% of the time in low stage, enhancing
efficiency and comfort with lower humidity levels and quieter operation. It’s like getting two air
conditioners or heat pumps in one system.
* UL: Stands for Underwriters Laboratories, an impartial, non-profit organization that tests and rates
electrical products for public safety.
* Upflow Air Conditioner: A type of air conditioning system that discharges air into the conditioned
space through a top-mounted discharge plenum or an overhead duct system.
* Upflow Furnace: A furnace that pulls return air in from the bottom and expels warm air from the top
into the duct work. This type of furnace is usually installed in a basement or an out-of-the-way closet.
* Vacuum Pump: A pump used to remove air and moisture from a refrigeration system.
* Vapor Seal: A barrier that prevents air, moisture, and contaminants from migrating through tiny
cracks or pores in the walls, floor, and ceiling into a room. Vapor seals may be created using plastic
film, vapor-retardant paint, vinyl wall coverings and vinyl floor systems.
* Ventilation: The process of supplying or removing air, by natural or mechanical means, to or from
any space. Such air may or may not have been conditioned.
* Ventilator: A devices that captures heating or cooling energy from stale indoor air and transfers it to
fresh incoming air.
* Water Cooled System: A type of air conditioning system that uses freon as a refrigerant and water as
a condensing medium. Typically, the water-cooled condenser is located inside the air conditioner with
the rest of the refrigeration components. Water is piped to the unit from an external source.
* Zoning: A way to increase your home comfort and energy efficiency by controlling when and where
heating and cooling occurs. Programmable thermostats control the timing of when your equipment
operates; dampers are used to direct air flow to certain sections or “zones” of your home.
All rights reserved. Absolute Climate Control, 2010
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